Whoever adapted this for the film did a stellar job. The plot in the book is almost the same, with a few details altered and minor characters who've been omitted in the film, but they're roughly the same story. The ending of the book seems rather unlikely and a bit far-fetched, whereas the same ending in the film just looks impossible.
But it's like reading the Financial Times. Part of that might be the fault of a rather pedestrian translation. Maybe it sparkles in Swedish.
Is all detective fiction like this? I haven't read much. Maybe it's one of the conventions of the genre that you're supposed to drown the reader in tedious details.
Save yourself the bother. See the film instead, which is short, sharp and sexy. If you'd like to read a novel about awful serial killing type stuff, try (my friend) Ruth Newman's wonderful Twisted Wing, just reissued in a new paperback version.